1. Field of the Invention
The present invention relates to a method and an apparatus for extracting fats and oils from animal or vegetable oil-bearing materials including soybean, rapeseed, sunflower, corn, and the like.
2. Background of the Related Art
Several types of edible oil extractors have been known such as the De Smet and the Lurgi extractors which are shown in FIGS. 5A and 5B, respectively.
The De Smet extractor shown in FIG. 5A has a structure in which the raw materials for extraction are loaded on and conveyed by a rotary metal-mesh conveyor 108, and solvent or miscella (i.e., a mixture of solvent and extracted oil) is sprayed over the raw materials in a manner to provide countercurrent flow extraction. The miscella receiving hoppers 115, into which the miscella flows down from the mesh conveyor, are located between the carrying and the returning stages of the rotary metal-mesh conveyor, and this inevitably increases the size of the extractor.
Further, the hoppers and the adjacent parts or elements are easily subject to corrosion, since they are positioned within the casing 101 of the extractor. Additionally, the metal-mesh of the conveyor is often stopped up or clogged by fine particles of the raw materials, and accordingly the returning stage of the conveyor must always be sufficiently washed by solvent during the operation. It is also necessary to clean the mesh conveyor at least once a year in a troublesome way.
The Lurgi extractor, which is shown in FIG. 5B, is rather complicated in structure and has and endless framed belt 208 which is supported by a two-stage endless sieve belt. The extraction is carried out in both the going and returning stages. In this case, the extractor is apt to be of a large size, since the height of the casing 201 should be larger than the total height of the upper and lower frames. The frames should have sufficient height to convey the necessary amount of raw materials held therein, and this is another reason the apparatus must be large-sized.